Tapping attachment for drill presses and other machines



G. PAWSON.

TAPPING ATTACHMENT FOR DRILL PRESSES AND OTHER MACHINES. APPLICATIONFILED NOV. 26. 1919.

Patented 00$. 31, 1922.

Mimessm AQ &

Patented Get. 31;, i922.

GILBERT PAWSON, OF LONDON, ENGLAND.

TAPPING ATTACHMENT FOR DRILL PRESSES AND OTHER MACHINES.

Application filed November 26, 1919. Serial No. M0323.

To all whom it may concern Be it known that I, GILBERT Pawson, a subjectof the King of Great Britain, residing at Queens Gate Works, KensingtonGore, London, England, have invented new and useful Improvementsin'Tapping Attachments for Drill Presses and Other hilachines, of whichthe following is a specification.

My invention relates to tapping attachments such as are used inconnection with drilling and other machines tor automath :ally severingthe driving connection between the driving spindle and the-tap shouldthe latter, when entering a blind hole, strike the bottom of the saidhole or otherwise meet with a resistance which might cause the breakageof the tap and wherein provision is made for reversing the direction ofrotation for withdrawing the tap from the hole. Apparatus of this kindhas heretofore been constructed wherein the spindle carrying the toolholder is made in two parts capable of a certain amount of longitudinalmovement relatively to one another, in such a manner, that clutch memberon the longitudinal moving part will be caused to engage either with aclutch part directly driven or with another clutch part driven throughthe medium of gearing, so thatthe.

clutch member when engaging with one clutch-part will be driven in onedirection and when in engagement with the other clutch part in theopposite direction, and wherein a friction clutch is provided totransmit the drive to the tap.

In practice, however, it is difficult to so adjust the friction clutchthat, on the one hand, it shall transmit the required torque withoutyielding and that, on the other My invention will be readily understoodby reference to the accompanying drawing, in which I 7 Figure 1 is asectional, elevation of: my improved tapping attachment.

Figure 2 is a plan, and

Figure is a section on the line 3- 3, Figure 1. t

Figure at is a view of certain of the parts shown in Figure 3 but in adifferent position.

a indicates the shank of the attachement which, as shown, is made ofcone shape to fit the socket or chuck on the spindle of a drillingmachine or lathe. 7) indicates a driving plate which is secured to thesaid shank and rotates therewith and (2 another plate, which. Iterm thedriven plate, which receives its motion from the driving plate and whichissecured to a sleeve (Z on the lower part of the spindle c, and carriesat itslower end a gear wheel e which rotates with the driven plate.

This gear wheel 0 engages with an idle gear wheel 7", mounted on. aspindle f in a gear box 9 on the sleeve (Zll616l11l)'f016 referred to.and on another spindle h in the said gear box is mounted another idlewheelv -27 which in turn engages with the idle wheel 7 and also withanother gear wheel 7' in the said gearbox. i i

Mounted. in the lower part of the said box {/is the tap holding or chuckspindle 7.1 the upper end of which projects into, and is capable of,sliding within a longitudinal hole in the spindle (0.

Upon the interior ot the gear wheel 6 is formed a number of clutch teethZ and upon the interior of the gear wheel f is formed another series ofclutch teeth m. and through the tool spindle 73 extends a clutch member0 which, when in engagement with the teeth Z of the wheel r2 will bedirectly driven from the plate 0, whilst when the said clutch member 0in engagement with the teeth m of the wheel f it will be driven in thereverse direction owing to the fact that the said gear wheel 7? willreceive its motion from the wheel 6 through the medium of the idlewheels f and Motion is transmitted from the driving plate I) to thedriven plate 0 through the medium of a series of levers p, p pivotallymounted upon the said driving plate I) and having connected to them atone end rollers or studs 21, p whilst at the other end the said levershave connected to them springs g which normally tend to draw the saidlevers up against stops g 9 the tension of these springs is adjustableby means of screws 1' in brackets'r Upon the driven plate 0 are formedabutments s with one end 8 of which, when the levers p are in theirnormal positions, the rollers or studs 19 will engage, so that as thedriving plate I) is rotated motion will be transmitted to the drivenplate 0 through the said studs 72*. The said ends 8 of the abutments sare soniewhat'inclined so that as the driving and driven plates arebeing rotated any abnormal resistance to the rotation of the tool willcause the studs 29 to slip off the said ends and move the levers p fromthe position shown in full lines in Figure 2 to that shown in dottedlines. This movement allows the studs 72 to slide quietly and with outshock along and past the inner inclined faces of the abutments s whenthe levers 7) again rest against their stops (1 ready to again take upthe drive whilst the driven plate 0 remains at rest, the springs (1being so adjusted that the strain exerted by the studs upon theabutments will be insufficient to break the tap or other tool held inthe chuck spindle in. Vhilst the driven plate 0 remains at rest. thelevers 7 will oscilla-te at each revolution of the said driving plate.When this takes place the operator, without stopping the rotation of thedriving plate I) lifts the drill spindle whereupon the clutch teeth Zare disengaged from the member 0 and the clutch teeth an engaged withthe said member, the latter being prevented from rising by theengagement of the tap ping tool with the work, so that, as hereinbeforestated, rotary motion in the reverse direction will be transmitted tothe spindle in through the gearing described, the gearing being soproportioned that this reverse movement will be atquicker rotation thanin the other direction.

In order that during this reverse movement a positive drive shall betransmitted to driven plate 0 I provide upon one of the levers 0 an armt carrying a stud u, the head.

4) of which is normally in contact with the periphery of the said drivenplate, as shown in Figure l, but which during the tapping operation isbelow the said plate 0 shown in Figure 4. The necessary longitudinalmovement between the driving and driven plates is provided for byarranging upon the said driving plate a. flanged ring w which engageswith a flange w on the spindle (it. During the tapping operation thepressure of the tap against the work being oper ated upon lifts the gearbox and the parts connected therewith so that the flange m is pressedupon by the plate 0 as shown in Figure at. lVhen, however, the tap isbeing reversed or backed. out the flange m bears beneath the flange ofthe ring to so that the head 4; is in the position shown in Figure l,and prevents! the levers 2), on which it is mounted, from moving fromthe full line position in Figure 2, so that the pin 1) thereon impartsapositive drive to the plate 0.

By my improved construction all strain is removed from the clutch andgear mechanism during the reversal of the tap thus allowing the clutchmember 0 to drop freely from engagement with the teeth I into engagementwith the teeth on; and the predetermined torque at which thcrclease gearoperates is not effected by changes of temperature, lubrication, wear ordirt as is the case in apparatus of the friction type.

Claims.

1. A tapping attachment comprising a chuck spindle, a driving plate anda driven plate, means whereby motion may be transmitted from saiddriving plate to said driven plate consisting of a series of leverspivotally mounted on said driving plate, said levers being actuated bysprings and having connected at one end thereof studs, which engageabutments on said driven plate, and means for throwing said studs out ofengagement with said abutments.

2. A tapping attachment as claimed in claim 3 in which the means forthrowing the studs out of engagement with the abutments, consists inproviding an inclined end on said abutments, whereby the studs may slipoff of said ends in case of any abnormal resistance to the tool.

A tapping attachment comprising a chuck spindle, a driving plate and adriven plate capable of limited movement towards and away from oneanother, means whereby motion may be transmitted from said drivmg plateto said driven plate consisting of a series of levers pivotally mountedon said driving plate, said levers being actuated by springs and havingconnected to one end thereof studs which engage abutments on said drivenplate, means for throwing said studs out of engagement with saidabutments when the driving plate is moved to wards the driven plate whentapping and means for preventing the. studs from being thrown out ofengagement with the abutments when the driven plate is lifted towardsthe driving plate when reversing.

4. A tapping attachment as claimed in claim 3, wherein the means forpreventing the studs on the levers from being thrown out of engagementwith the abutments, comprise a stud on one of the levers having anenlargement or head to contact with the periphery of the driven plate.

GILBERT PAlVSUN.

